Method for cracking organic matter in a cracking furnace tube

Abstract

The present application relates to the field of organic matter cracking, and discloses a method for cracking organic matter in a cracking furnace tube, which comprises the following steps: (1) feeding fluid into the cracking furnace tube; (2) causing short circuit of the cracking furnace tube to generate a short circuit current, so that the fluid is heated by the heat generated by the short circuit current and cracked; wherein the cracking furnace tube is conductive. The method uses the heat generated by the short circuit current to heat the fluid in the cracking furnace tube, and controls the temperature of the tube wall of the cracking furnace tube through voltage and current, so that the depth of the fluid cracking reaction can be controlled.

Description

Technical Field

[0001] This invention relates to the field of organic matter pyrolysis, and more specifically to a method for pyrolyzing organic matter in a pyrolysis furnace tube. Background Technology

[0002] Industrial ethylene cracking furnaces typically use a high-temperature flame and flue gas generated by the combustion of a mixture of fuel gas (mainly methane) and air to heat the furnace tubes. This process produces large amounts of carbon monoxide and carbon dioxide. Commonly used cracking furnaces employ traditional electric heating methods, which utilize the heat generated by energizing resistance wires to heat the air and refractory bricks surrounding the furnace tubes. The air and refractory bricks then further heat the furnace tubes. A significant portion of this heat is directly radiated from the resistance wires to the furnace tubes. This heating method has relatively low thermal efficiency, with less than 50% of the heat actually reaching the cracking reaction itself, and it is prone to coking during the cracking process. Summary of the Invention

[0003] The purpose of this invention is to overcome the technical problems of high carbon dioxide emissions, low thermal efficiency and easy coking in the prior art, and to provide a method for pyrolyzing organic matter in a pyrolysis furnace tube.

[0004] The inventors of this invention accidentally discovered in experiments that by using the heat generated by the short-circuit current to heat the fluid inside the pyrolysis furnace tube, and by controlling the tube wall temperature of the pyrolysis furnace tube through voltage and current, the depth of the fluid pyrolysis reaction can be controlled. Furthermore, no carbon dioxide is produced during the pyrolysis process, resulting in high thermal efficiency.

[0005] To achieve the above objectives, the present invention provides a method for pyrolyzing organic matter in a pyrolysis furnace tube, the method comprising:

[0006] (1) Fluid is introduced into the cracking furnace tube;

[0007] (2) Short-circuit the cracking furnace tube to generate a short-circuit current, thereby using the heat generated by the short-circuit current to heat the fluid and cause the fluid to crack;

[0008] The pyrolysis furnace tube is conductive.

[0009] According to the method for heating a pyrolysis furnace tube provided by the present invention, the method utilizes the heat generated by a short-circuit current to heat the fluid inside the pyrolysis furnace tube, and controls the tube wall temperature by controlling voltage and current, thereby controlling the depth of the fluid pyrolysis reaction. This method also has the following advantages:

[0010] (1) Using clean energy electricity as a heat source for the pyrolysis reaction can greatly reduce carbon emissions during the pyrolysis process;

[0011] (2) The organic matter of the present invention does not require the combustion of substances containing carbon, nitrogen and sulfur to provide heat during the pyrolysis process, thus reducing the emissions of carbon dioxide, nitrogen oxides and sulfides;

[0012] (3) Direct power supply results in high heat utilization and low heat loss. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of a pyrolysis furnace according to a preferred embodiment of the present invention;

[0014] Figure 2 This is a schematic diagram of the organic matter pyrolysis device in Comparative Examples 1-8 of the present invention.

[0015] Explanation of reference numerals in the attached figures

[0016] 100 Liquid Mass Flow Meter, 200 Gas Mass Flow Meter, 300 Preheating Equipment, 400 Pyrolysis Furnace, 500 Quenching Equipment, 600 Water Cooling Equipment, 700 Ice Cooling Equipment, 800 Buffer Equipment, 900 Humidification Equipment, 1000 Wet Gas Flow Meter, 401 Furnace Tube, 402 Electrode, 403 Temperature Detection Equipment, 404 Insulation Layer Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] This invention provides a method for pyrolyzing organic matter in a pyrolysis furnace tube, the method comprising:

[0019] (1) Fluid is introduced into the cracking furnace tube;

[0020] (2) A short circuit is generated in the pyrolysis furnace tube to produce a short circuit current, thereby using the heat generated by the short circuit current to heat the fluid (to make it reach the pyrolysis temperature) and cause the fluid to pyrolyze;

[0021] The pyrolysis furnace tube is conductive.

[0022] In this invention, in order to ensure that the current can generate a large amount of heat in the furnace tube, preferably, the resistivity of the pyrolysis furnace tube at 20°C is not greater than 5 ohm-meters.

[0023] In this invention, in order to ensure that the inner wall temperature is 700-1000℃ and that the reaction provides sufficient energy, the outer wall temperature of the pyrolysis furnace tube is preferably 900-1300℃.

[0024] In some embodiments of the present invention, in order to ensure that the pyrolysis depth of various pyrolysis raw materials meets the requirements, the pyrolysis temperature is preferably 750-900℃.

[0025] In this invention, the pyrolysis pressure is preferably 0.05-0.2 MPa. The mass ratio of water to organic matter is preferably 0.5-0.8.

[0026] In some embodiments of the present invention, the pyrolysis furnace tube is not particularly limited, as long as it is conductive. Preferably, the pyrolysis furnace tube is a metal pyrolysis furnace tube (e.g., Cr20Ni80 resistance heating alloy) or a pyrolysis furnace tube with MoSi2 as the main component (the pyrolysis furnace tube also includes a reinforcing agent, the volume ratio of MoSi2 to the reinforcing agent being 1-9:1), and the particle size of the reinforcing agent is not greater than 5 micrometers. The particle size of the MoSi2 is preferably not greater than 10 micrometers. Reference Figure 1 To maintain the temperature of the pyrolysis furnace tubes, an outer insulation layer 404 is provided, which is selected from heat-insulating materials such as asbestos and refractory bricks. The arrangement of the pyrolysis furnace tubes is not limited; for example, they can be arranged horizontally or suspended. The pyrolysis furnace tubes also include a temperature detection device 403, the type of which is not limited and can be a thermocouple.

[0027] In this invention, when the pyrolysis furnace tube is a metal pyrolysis furnace tube, a low-voltage alternating current is applied to the metal pyrolysis furnace tube to induce a short-circuit current. Preferably, the frequency of the low-voltage alternating current is 50Hz; the voltage is preferably 0.1-25V. More preferably, the short-circuit current is 20-60A. When the pyrolysis furnace tube is a MoSi2-containing pyrolysis furnace tube, a high-voltage alternating current is applied to the MoSi2-containing pyrolysis furnace tube to induce a short-circuit current. Preferably, the frequency of the high-voltage, high-current alternating current is 50Hz; the voltage is 100-500V. More preferably, the short-circuit current is 0.4-1A. The alternating current is provided by a transformer and connected to the pyrolysis furnace tube 401 through electrode 402.

[0028] To ensure sufficient pyrolysis depth, the heat is preferably 21000-85000 J / h.

[0029] In some embodiments of the present invention, in order to improve the thermal efficiency of the pyrolysis furnace, the length-to-diameter ratio of the furnace tube 401 is preferably 5-2000.

[0030] In some embodiments of the present invention, in order to ensure that the heat generated by the current can be effectively transferred to the internal fluid, the furnace tube should not be too thick. Preferably, the thickness of the furnace tube is 0.1-30 mm.

[0031] In this invention, within the defined range of furnace tube thickness, the temperature difference between the inner and outer walls of the pyrolysis furnace tube is 200-500℃.

[0032] In some embodiments of the present invention, the fluid is an organic substance, preferably a hydrocarbon. For example, it can be naphtha and / or diesel oil.

[0033] The present invention will be described in detail below through examples. The pyrolysis furnace tubes used in the examples and comparative examples, and the relevant parameters of the pyrolysis reaction, are shown in Tables 1 and 2. Specifically, the materials of the furnace tubes in Examples 1-4 are shown in Table 1; the materials of the pyrolysis furnace tubes in Examples 5-8 are Cr20Ni80 resistance heating alloy; and the materials of the furnace tubes in Comparative Examples 1-8 are all 2520 alloy.

[0034] Table 1

[0035]

[0036] Note: In Table 1, " / " indicates that there is no relevant data.

[0037] Table 2

[0038]

[0039] Note: In Table 2, " / " indicates that there is no relevant data.

[0040] Comparative Examples 1-8

[0041] All pyrolysis tests were conducted at Figure 2 The process is carried out on the device shown, and the specific procedures are as follows: First, the raw material oil and water are controlled by the liquid mass flow meter 100 to enter the constant temperature preheater 300 (resistance wire heating) at the mass ratios shown in Table 2. After vaporization, they enter the high temperature pyrolysis furnace 400. The relevant parameters of the furnace tube are shown in Table 1. The length of the constant temperature zone of the furnace tube is about 50cm. The furnace tube is heated by three sections of resistance wire. The temperature of the tube wall is kept constant at the set value by the PLC, thereby controlling the outlet temperature COT of the pyrolysis gas. The specific operating parameters are shown in Table 2. The product from the pyrolysis furnace passes through a quench cooler 500 (cooling medium: 20°C water; discharge temperature: 100-200°C), a water-cooled tank 600 (cooling medium: 20°C water; discharge temperature: 20-50°C), an ice-cooled tank 700 (cooling medium: water below 5°C), a buffer bottle 800, a humidification bottle 900 (water level in the humidification bottle is 80% of the bottle's height), and a wet gas flow meter 1000 before being vented. A pyrolysis gas sample is taken from the buffer bottle 800, and the volume percentage of each component is analyzed by gas chromatography. The heat source is the combustion of a mixture of N2 and O2, with the flow rates of N2 and O2 controlled by a gas flow meter 200. The pyrolysis results obtained from Comparative Examples 1-8 are shown in Tables 3 and 4.

[0042] Examples 1-8

[0043] The embodiments of the present invention will Figure 2 The electric heating furnace 400 of the device shown is in operation. Figure 1 The modification shown replaces the resistance wire heating method with direct low-voltage AC current supplied to the wall of the pyrolysis furnace tube. The heat generated by the short-circuit current heats the fluid inside the tube. The tube wall temperature is controlled by voltage and current, thus controlling the depth of the fluid pyrolysis reaction. The outer wall of the furnace tube is wrapped with refractory cotton, and the wrapped tube is placed in an insulated shell made of refractory bricks. Specifically, the raw material oil and water are first fed into the constant-temperature preheater 300 (resistance wire heating) at the mass ratios specified in Table 2, controlled by the liquid mass flow meter 100. After vaporization, they enter the pyrolysis furnace 400. Relevant furnace tube parameters are shown in Table 1. The length of the constant-temperature zone of the furnace tube is approximately 50 cm. Low-voltage AC current is supplied by a transformer; AC current parameters are shown in Table 2. The PLC maintains the tube wall temperature at a set value, thereby controlling the outlet temperature (COT) of the pyrolysis gas. Specific operating parameters are shown in Table 2. The product from the pyrolysis furnace passes through a quench cooler 500 (cooling medium: 20°C water; discharge temperature: 100-200°C), a water-cooled tank 600 (cooling medium: 20°C water; discharge temperature: 20-50°C), an ice-cooled tank 700 (cooling medium: water at a temperature below 5°C), a buffer bottle 800, a humidification bottle 900 (water level in the humidification bottle is 80% of the bottle's height), and a wet gas flow meter 1000 before being emptied. A pyrolysis gas sample is taken from the buffer bottle 800, and the volume percentage of each component is analyzed by gas chromatography. Embodiments of this invention are performed on this device; relevant parameters of the furnace tubes are shown in Table 1.

[0044] By precisely controlling the transformer current using a PLC, the outer wall temperature of the furnace tube can be kept constant at the required value, thereby controlling the outlet temperature (COT) of the pyrolysis gas, as shown in Table 2. Furthermore, the temperature differences between the inner and outer walls in Examples 5-8 are 200℃, 250℃, 300℃, and 500℃, respectively. The results obtained after pyrolysis are shown in Tables 3 and 4.

[0045] Table 3

[0046]

[0047] Table 4

[0048]

[0049] Furthermore, in Examples 1-4, the resistivity of MoSi2 is approximately 1 ohm-meter. Combined with the cross-sectional area and length of the furnace tube, the resistance of the furnace tube can be calculated to be approximately 425 ohms. By controlling the current flowing through the furnace tube, approximately 244,800-1,530,000 J of heat can be obtained per hour. In Examples 5-8, the resistivity of the chromium-nickel alloy is 1 × 10⁻⁶. -6Based on the ohm-meter value and the cross-sectional area and length of the furnace tube, the resistance of the furnace tube can be calculated to be 0.148 ohms. By controlling the current flowing through the furnace tube, approximately 21,000-85,000 J of heat can be obtained per hour. According to relevant estimates, each gram of naphtha requires approximately 200 J of heat for cracking. In this experiment, 100 grams of naphtha are processed per hour, requiring approximately 20,000 J of heat (excluding heat loss). Therefore, controlling the current between 20-60 A provides sufficient heat for the cracking reaction. According to relevant estimates, with a furnace tube inner diameter of 10 mm and a wall thickness of 1.5 mm, the temperature difference between the inner and outer walls is approximately 300 °C when current flows through the furnace tube. Therefore, if the inner wall needs to reach approximately 850 °C (close to COT), the outer wall needs to reach approximately 1150 °C. The heat utilization rates achieved in the examples and comparative examples are shown in Table 5.

[0050] Table 5

[0051] serial number Heat utilization rate / % Example 1 60％ Example 2 55％ Example 3 62％ Example 4 57％ Example 5 54％ Example 6 61％ Example 7 58％ Example 8 60％ Comparative Example 1 30％ Comparative Example 2 35％ Comparative Example 3 32％ Comparative Example 4 38％ Comparative Example 5 30％ Comparative Example 6 40％ Comparative Example 7 37％ Comparative Example 8 29％

[0052] As can be seen from Tables 3-5, the method of this invention for pyrolyzing organic matter achieves a depth of pyrolysis comparable to that of conventional methods. However, Examples 1-8 do not produce carbon dioxide or exhibit coking during the pyrolysis process, demonstrating good equipment safety and high thermal efficiency. In contrast, Comparative Examples 1-8 all exhibit varying degrees of coking.

[0053] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for pyrolyzing organic matter in a pyrolysis furnace tube, characterized in that, The method includes: (1) Fluid is introduced into the cracking furnace tube; (2) A short circuit is generated in the pyrolysis furnace tube to produce a short circuit current, thereby using the heat generated by the short circuit current to heat the fluid and cause the fluid to pyrolyze; The pyrolysis furnace tube is conductive; The fluid is an organic compound; The pyrolysis furnace tube is a pyrolysis furnace tube with MoSi2 as the main component; A high-voltage alternating current is applied to the pyrolysis furnace tube, which is mainly composed of MoSi2, to induce the short circuit. The voltage of the high-voltage alternating current is 100-500V, and the short-circuit current is 0.4-1A.

2. The method according to claim 1, characterized in that, The resistivity of the pyrolysis furnace tube at 20°C is no greater than 5 ohm-meters.

3. The method according to claim 1, characterized in that, In step (2), the pyrolysis temperature is 750-900℃.

4. The method according to any one of claims 1-3, characterized in that, The length-to-diameter ratio of the pyrolysis furnace tube is 10-2000.

5. The method according to any one of claims 1-3, characterized in that, The thickness of the furnace tube is 0.1-30mm.

6. The method according to any one of claims 1-3, characterized in that, The fluid is a hydrocarbon.

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